It is conceivable that passengers of an elevator car or cage may suffer injuries if the elevator cage should abruptly move downwardly or upwardly due to accidents or the like which may occur when the passengers are getting on or off the elevator cage or due to a fault of a brake of a hoisting machine, malfunction of an electric control system and others. As the measures for coping with occurrence of such unwanted situations or events, an emergency stopping apparatus or a speed governor has heretofore been installed in association with a balance weight or a rope brake designed for directly gripping a main rope has been installed internally of a machine room. These conventional emergency brake apparatuses known heretofore will be reviewed below.
FIG. 7 is a front view showing a conventional brake apparatus for an elevator system which is disclosed, for example, in Japanese Patent Application Laid-Open Publications No. 199483/1994. This known brake apparatus includes a wedge-like brake member 33 which is adapted to be pushed into between a direction inverting wheel 31 and a pressing member 32 when brake is applied, wherein upon application of the brake, the brake member 33 is pushed or pressed against the direction inverting wheel 31 by means of a coned disk spring 34 through the medium of the pressing member 32 to cause a rope 35 to be gripped or sandwiched between the direction inverting wheel 31 and the brake member 33 for thereby stopping the cage.
FIG. 8 is a sectional view of a conventional emergency brake apparatus which is disclosed, for example, in Japanese Patent Application Laid-Open Publication No. 193860/1993. This known emergency brake apparatus includes a brake element 43 implemented in the form of a star wheel and mounted rotatably on a shaft 42 of a driving rope pulley 41 juxtaposed in contact therewith. The brake element 43 is constantly pressed against an annular end surface portion 41a of the driving rope pulley 41 by means of a cup-shaped spring 44 so that the brake element can ordinarily rotate together with the driving rope pulley 41.
Upon occurrence of overspeed in the upward moving direction of the elevator cage, a trigger mechanism 45 is put into operation to push forwardly a braking bolt 46 into an inter-spoke space of the star-wheel-like brake element 43 to thereby prevent rotation of the brake element 43. As a result of this, sliding takes place between the annular end surface portion 41a and the brake element 43 pressed thereagainst, whereby a braking torque of magnitude appropriate for the driving rope pulley 41 is produced. This braking torque is extraordinary or incommensurably greater than the braking torque generated in the ordinary brake manipulation.
The conventional emergency brake apparatuses described above can certainly be designed to be put into operation when the elevator cage abruptly starts to move downwardly or upwardly to stop the movement of the elevator car or cage for thereby protecting the passengers against injury.
However, the conventional emergency brake apparatuses for the elevator system of the structures described above suffer problems that a large space for installing the brake apparatus in the machine room or other is required, that the main rope may undergo damage, that the brake apparatuses are very expensive because of complicated structures, and so forth.
Furthermore, the conventional apparatuses shown in FIGS. 7 and 8 suffer an additional problem that although they are effective for the upward movement at a speed higher than the rated one, it is impossible to prevent occurrence of accident due to unexpected or abrupt movement of the elevator cage in the downward or upward direction from the stationary state.
With this invention, it is contemplated as an object thereof to solve the problems mentioned above by providing an emergency brake apparatus for the elevator system which requires especially any additional space for installation in a machine room or the like and which is capable of preventing abrupt movement of the elevator cage in the downward direction or upward direction while protecting the rope from damage with a simplified structure capable of being manufactured inexpensively.